Arduino Ide isn't run and Board manager couldn't find esp8266 javaNull problem

Arduino Ide is closing while it is opening so I have Deleted Arduino15 directory. Then I could run Ide new. Then I try to add preferecnces “http://arduino.esp8266.com/stable/package_esp8266com_index.json” link for Esp8266 12e Nodemcu. then open Board manager and try to find Esp8266 but warned me “java.lang.NullPointerException”. Then I closed Ide and try to reopen so It didnt open again. when I delete Arduino15 It is opening again. I delete old java and renew them, I was working by Id 1.8.8 and I unloaded it then I downloaded 1.8.12 now. But what I did, the problem is going on still.

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Then ensure you are or were not affected.

Ok. I found the problem. Maybe you need sone day so I'm writting here. Run Windows->start->run->regedit then find 'arduino' key, tag etc. And delete all the finded things could do. Restart windows. If you sol ve your problem bu this method pls inform me too.